Since this is 91, its likely that the original engine has been replaced, and various other mods have been done. Essentially you need ot figure out what the previous owner did, and either fix it or ignore it.
A common "trick" with the wiring is to change the MAF sensor (on the air filter can) around to get more fuel at high boost. Pull off the 8 pin connector and check for bent pins. Check for 5V (NOT +12v) on one of the pins, as this is the MAF sensor supply voltage.
Other issues are the coolant temp sensor (2 pin sensor with black? connector on the themostat housing) connection.
If the temp sensor is not properly connected, or the wrong sensor for the engine, it will be hard to start esspecially when cold.
If possible, verify what ECU is fitted. The 90-91 ECU has slightly different pin connections to the 92-94.
You may also have fuel pump relay issues. This is the large can in the center console, near the ECU.
Open the ECU and check the large electrolytic capacitors for leaks. Its a common problem, and there various people around who will replace them before they destroy the ECU board.
Check all the vacuum hoses for cracks and leaks. Check the hoses for the intercooler and up to the throttle body.
Have a look at www.lancerproject.ca
for more information.